In the copending application of William R. Hoskinson for "Digital Control Of Attack And Decay" Ser. No. 917,308, filed June 20, 1978 assigned to the same assignee as the present application, namely The Wurlitzer Company of DeKalb, Ill. circuits are disclosed for utilizing digital signals of variable duty cycle to control the attack and decay of an electrical wave representing a musical tone. In accordance with that disclosure once suitable adjustments are made to the musical instrument the attack characteristics and the decay characteristics remain fixed until further adjustments are made.
There are times, the simulation of piano tones being a specific example, in which it may be desired to have a very slow decay time, i.e. a long sustain, as long as a key is held depressed. However, immediately upon release of a key it is desired that the tone should decay very rapidly.